During a flight between San Francisco to Hong Kong, staff reportedly spotted an explosion before debris fell back to earth.

It’s believed flight CX893 was flying over Japan when the missile was launched by North Korea.

While a message to staff via company intranet sent by manager of operations and former chief pilot Mark Hoey said: ‘Today [November 29] the crew of CX893 reported “Be advised, we witness the DPRK missile blow up and fall apart near our current location.

(Picture: Daily Mail)

An Hwasong-15 intercontinental ballistic missile, at an undisclosed location in North Korea (Picture: AP)

‘We advised ATC [air traffic control] and ops [operations] normal. Just letting you know’. Looking at the actual plots, CX096 might have been the closest, at a few hundred miles laterally.’

General Sir Richard Barrons, the former commander of Joint Forces Command, said: ‘We are looking at North Korea which within the next 18 to 20 months will mate a nuclear missile to an intercontinental-range ballistic missile which can reach London. We can’t deal with that.’

He added that years of cuts to defence budgets have created ‘existential risks’ to the UK, which the armed forces would be unable to deal with and that without more resources there was a danger it would simply ‘fall over’ in the face of a foreign attack.